For many years, schizophrenic thought disorder has been regarded as being due to an abnormality of concept formation of some sort. However, there has not been general agreement about the nature of this abnormality. Kurt Goldstein and his followers (9, 32, 33) have argued that schizophrenics are abnormally “concrete”. That is to say, they are unable to perform inductive reasoning, since they are unable to make an abstract generalization. Norman Cameron (11, 12, 13, 14, 15, 16, 17, 18, 19) on the other hand argues that in one sense at least, schizophrenic concepts are over-generalized. He believes that the concepts formed by schizophrenics are “over-inclusive”. They are unable to maintain the normal conceptual boundaries, and incorporate into their concept elements (some of them personal) which are merely associated with the concept, but are not an essential part of it. This makes their thinking both over-general, and less precise than normal. A large number of studies have been carried out to test both these hypotheses.